You can still postpone updates, but yes, they've got more pushy than in the past. The issue is that iOS is the priority, and that has to be updated every year to support new models; so MacOS is also pushed to update in order to keep integrated systems (e.g. notes) in sync. This said, one can simply postpone upgrades indefinitely and just ignore the bits that break. I don't really use most of them, so I'm still not on the latest release despite it having been released some 6 months ago.